The present invention relates generally to new and novel improvements in thermally transferable printing ribbons and methods of making same. More particularly, the present invention relates to thermally transferable printing ribbons and methods of making same which are fabricated by obtaining, mixing and grinding solid ingredients together, and then emulsifying the entire mixture.
The usual method of making aqueous thermally transferable printing ribbons is to first purchase or make the emulsified ingredients, and then to mix the various emulsified ingredients together. A typical pre-emulsified thermally transferable printing ribbon formulation includes one or more emulsified waxes, one or more emulsified resins, and pigments. The pre-emulsified ingredients are mixed with the pigments, and then the resultant mixture is ground in an attritor or ball mill. The resulting formulation is then coated onto an elongated backing element.
Mixing pre-emulsified ingredients together results in a formulation containing discrete particles of wax, particles of resin, and particles of pigment suspended in water. All of these components are solids and have very little opportunity to interact with each other. This inability for ingredients to mix and interact with each other results in several undesirable consequences for thermally transferable printing ribbon formulations.
First, during the grinding of pre-emulsified thermally transferable printing ribbon formulation components, the solid resin particles cannot act as dispersants for the pigment. Resins must be in a liquid form to interact with pigments. This results in a low color density for printed images and characters.
Second, emulsions consist of particles suspended in water. Once the water is removed, the particles remain. The mixing of two or more emulsions results in two or more distinct types of particles, resulting in non-uniform coating on the elongated backing element and physical separation of the ingredients from each other on the elongated backing element.
Accordingly, an object of the present invention is the provision of thermally transferable printing ribbons and methods of making same which provides a more uniform mixing and distribution of the solid ingredients in the thermally transferable printing media layer.
Another object of the present invention is to provide thermally transferable printing ribbons and methods of making same which provide printed images and characters having enhanced color density.
These and other objects of the present invention are attained by the provision of thermally transferable printing ribbons and methods of making same fabricated by initially mixing and grinding solid ingredients together, and then emulsifying the entire mixture. Thermally transferable printing ribbons formulations in accordance with the present invention generally include one or more waxes, one or more resins, and pigments. These ingredients are ground hot in an attritor or ball mill. This mixture is then emulsified, and the resulting formulation is coated on an elongated backing element utilizing conventional coating equipment and techniques.
Other objects, advantages and novel features of the present invention will become apparent in the following detailed description of the invention when considered in conjunction with the accompanying drawings.